Fernando Brice Olivier Ogadi, 35, left the Democratic Republic of the Congo in 2004 to escape political upheaval and came to South Africa.
Ogadi, a passionate maths teacher, worked as a car guard in the parking lot of the Zomerlust Spar in Paarl, Beeld newspaper reported.
He put up a rudimentary blackboard and would enthusiastically explain mathematical equations to any shoppers who cared to listen.
"If somebody is so passionate about something that he's prepared to leave his country for it, he deserves to be helped," said Sunward Park headmistress Ansie Peens.
"Not everybody has the ability to explain maths, but his method is quite unique," she said.
Ogadi started his new job on Monday morning, and has been given accommodation in the boarding school, where he offers extra classes and tuition in the afternoons.